Yolk sac tumor

Definition

A rare germ cell tumor characterized by multiple patterns reflecting endodermal extraembryonal differentiation (secondary yolk sac and allantois) or endodermal somatic tissues (intestine, liver, and mesenchyme). The tumors most commonly occur in the second or third decade of life. They are typically located in the gonads, occasionally also in other regions. Patients present with a pelvic mass and/or abdominal pain (females) or an often painless, unilateral testicular mass (males). Elevated serum alpha fetoprotein is a common laboratory finding.